A phased array antenna is known as an antenna for scanning a directional beam without physically moving an antenna. The phased array antenna is composed of a plurality of antenna elements. Each of the antenna elements is connected with a phase shifter. Each phase shifter alters a phase of a radio wave emitted from corresponding one of the connected antenna elements. By the phase shifter controlling a phase shift amount of the antenna element, the phased array antenna is able to scan a directional beam. For example, PTL 1 discloses a directivity-controllable array antenna. In addition, PTL 2 discloses a phase-tunable antenna feed network.
PTL 3 discloses a configuration of a phased array antenna in which each antenna element is connected with a variable capacitor. The phased array antenna described in PTL 3 alters a phase of a radio wave emitted from the antenna element by varying a value of the variable capacitor. By thus controlling a phase shift amount of each of the antenna elements, the phased array antenna described in PTL 3 scans a beam.
PTL 4 discloses a configuration of a phased array antenna equipped with two or more element groups, each of which includes two or more antenna elements having variable reactance elements. The phased array antenna described in PTL 4 alters a phase of the antenna element by varying a value of a variable reactance. By thus controlling a phase shift amount of each of the antenna elements, the phased array antenna described in PTL 4 scans a beam.